This invention relates to generally to overhead conveyor systems and more particularly to systems making use of an enclosed track in which a trolley is arranged to roll to support something from the trolley
Enclosed track conveyor systems are commonly used to support and carry items from a wheeled trolley located within the interior of an enclosed track. As is known enclosed tracks are hollow members having a top-wall, a pair of side walls projecting downward from the top wall and a pair of marginal flanges extending horizontally from respective ones of the side walls. The flanges are spaced from each other to form a slot therebetween. The trolley is located within the interior of the track, with its wheels or rollers disposed on the interior (upper) surface of the flanges.
Examples of enclosed track systems including internally located trolleys for rolling down the interior of the track are found in U.S. Pat. No. 3,589,503 (Leach), U.S. Pat. No. 3,627,595 (Leach) and U.S. Pat. No. 6,450,326 (Hoffmann et al.). The trolleys of the foregoing patents are arranged so that they can negotiate curves in the track.
In some prior art system, the movement or rolling of a trolley down the interior of an enclose track is accomplished by use a tractor drive that is mounted on the trolley, but located outside of the track. Such tractor drives make use of a drive wheel which extends through the slot in the track to frictionally engage the inner surface of the top wall of the track. The drive wheel is rotated by a motor mounted on the externally located tractor. This arrangement requires that the drive wheel be of a relative large diameter. As a result such tractors are not suitable for use in systems wherein the enclosed track includes a relatively small radius curve, since the drive wheel would engage or bind in the slot. While some enclosed track systems make use of tractors having drive wheels that engage and ride on the bottom of the track, i.e., the inner surface of one or more of the flanges, such systems are not practical due to splices used on the track, which results in an uneven drive surface, and make it difficult to keep a constant pressure on the drive wheel.
Thus, the design of existing hoist trolley drives makes it impractical to drive a trolley through a curve in an enclosed track system and a need exists for an enclosed track system which achieves that end.
This invention entails an enclosed track system comprising an enclosed track having at least one curved portion and a trolley arranged to roll within the interior of the enclosed track. The enclosed track is an elongated hollow member having a top wall portion, a pair of side wall portions and a pair of flanged portions. The flanged portions are spaced from each other to define a slot therebetween extending longitudinally along the track. The trolley comprises a rolling section and a drive section.
The rolling section comprises first and second roller portions. The first roller portion is located within the track and comprises at least one support roller arranged to roll on at least one of the flange portions of the track. The second roller portion is located within the track and comprises a drive wheel arranged to roll on the top wall portion of the track. The second roller portion is spaced longitudinally from the first roller portion. The drive section is located outside of the track and includes an articulated joint coupling the first roller portion to the second roller portion. The drive section is arranged to cause the drive wheel to rotate and roll along the top wall portion of the track, whereupon the drive wheel causes the trolley to move along the track. The articulated joint enables the first roller portion to pivot longitudinally with respect to the second roller portion to enable the trolley to negotiate curves in the track.